1. Field of the Invention
The present invention relates to agricultural harvesting systems in general and more particularly to a system for the selective collection of plant growth commonly known as biomass.
2. Discussion of the Related Art
In recent years our society and the world in general has become increasingly more and more energy dependent. The resulting rise in energy demands have coupled with rising costs for petroleum based fuels to kindle an increased interest in alternative fuels that once may have been considered too costly to produce. Of particular interest are fuel sources that are considered to be ‘renewable.’ One of these renewable and alternative energy sources is commonly referred to as biomass.
Biomass generally includes living and recently dead biological material which can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibers, chemicals or heat. Biomass may also include biodegradable wastes that can be burned as fuel, but it excludes organic material which has been transformed by geological processes into substances known as fossil fuels such as coal or petroleum.
Typical sources of biomass include several plants such as miscanthus, switchgrass, hemp, corn, poplar, willow and sugarcane. The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing. While the term biomass is also useful to identify plants where some of the plant's internal structures may not always be considered living tissue, such as the wood of a tree, and even though this biomass was produced from plants that convert sunlight into plant material through photosynthesis, the use of the term ‘biomass’ herein is by definition limited to agricultural plant growth that is harvested on a regular and periodic basis as part of an agricultural enterprise.
A major source of this biomass results from agricultural activities wherein the plant growth is produced specifically as a biomass product or alternatively is the residue of grain based agricultural crops. Traditionally, agricultural crop residues have been left on the field and reworked into the field's topsoil layer with the intent to return those nutrients removed during the crop's growth cycle and stored in the residue. Studies have revealed that sufficient and even optimal tilth levels in the topsoil layer can be maintained by returning only a fraction of the agricultural crop residue from a particular growth cycle. Until recently, there has been no particular incentive to remove the excess residue from agricultural fields other than for other agricultural uses such as bedding materials or low grade feed for agricultural livestock. However, with the interest in biomass as a renewable energy source, biomass can also now be considered an additional income source from the agricultural growth cycle to supplement the income derived from the harvested grains.
The desire to also harvest biomass from agricultural fields is tempered by the necessary caution to refrain from removing an excess of biomass and thus gradually depleting the topsoil nutrient levels after successive years of harvests. The nutrient needs of the topsoil vary geographically and even vary within the boundaries of a particular field such that determining harvestable quantities is location specific problem and not governed by general parameters applicable across an entire field. Such determinations must be made by an intelligent system that analyzes the topsoil layer concurrent with the harvesting of the biomass.
Thus, what is desired is a biomass harvesting system that efficiently removes the maximum quantity of biomass from a field while leaving sufficient biomass to minimize wind and water erosion and maintain soil tilth.